Casein Kinases I and 2α Phosphorylate Oryza Sativa Pseudo-Response Regulator 37 (OsPRR37) in Photoperiodic Flowering in Rice

Abstract

Flowering time (or heading date) is controlled by intrinsic genetic programs in response to environmental cues, such as photoperiod and temperature. Rice, a facultative short-day (SD) plant, flowers early in SD and late in long-day (LD) conditions. Casein kinases (CKs) generally act as positive regulators in many signaling pathways in plants. In rice, Heading date 6 (Hd6) and Hd16 encode CK2α and CKI, respectively, and mainly function to delay flowering time. Additionally, the major LD-dependent floral repressors Hd2/Oryza sativa Pseudo-Response Regulator 37 (OsPRR37; hereafter PRR37) and Ghd7 also confer strong photoperiod sensitivity. In floral induction, Hd16 acts upstream of Ghd7 and CKI interacts with and phosphorylates Ghd7. In addition, Hd6 and Hd16 also act upstream of Hd2. However, whether CKI and CK2α directly regulate the function of PRR37 remains unclear. Here, we use in vitro pull-down and in vivo bimolecular fluorescence complementation assays to show that CKI and CK2α interact with PRR37. We further use in vitro kinase assays to show that CKI and CK2α phosphorylate different regions of PRR37. Our results indicate that direct posttranslational modification of PRR37 mediates the genetic interactions between these two protein kinases and PRR37. The significance of CK-mediated phosphorylation for PRR37 and Ghd7 function is discussed.

The rice zebra3 (z3) mutation disrupts citrate distribution and produces transverse dark-green/green variegation in mature leaves

“…Photosynthesis-related proteins were detected as previously described, with some modifications (Han et al 2012 ; Kwon et al 2015 ; Kwon et al 2017 ). Leaf tissue (10 mg) was homogenized with 100 μL of SDS-PAGE sample buffer [50 mM Tris pH 6.8, 2 mM EDTA, 10% ( w / v ) glycerol, 2% SDS, and 6% 2-mercaptoethanol] and denatured at 100 °C for 5 min, then samples were subjected to SDS-PAGE.…”

The Importance of the Circadian Clock in Regulating Plant Metabolism

“…Two other key transcriptional activators of plant growth, phytochrome interacting factor 4 (PIF4) and PIF5, regulate consumption of sugars through the circadian clock [ 34 ]. These transcription factors are activated by the morning clock proteins LHY/CCA1 and are inhibited by the evening complex (EC), Early Flowering 3 (ELF3), ELF4, and lux arrhythmo (LUX) [ 34 , 35 ]. Thus, the LHY/CCA1 complex contributes to the regulation of carbon partitioning (through b) and starch degradation (through CaK) and the EC only regulates consumption [ 13 ] ( Figure 1 ).…”

The Rice Floral Repressor Early flowering1 Affects Spikelet Fertility By Modulating Gibberellin Signaling

“…In addition, it had been published that EL1 functions in GA signaling by demonstrating the in vitro phosphorylation of SLR1 (Dai and Xue 2010 ). EL1/CKI acts as a flowering repressor by interacting with and directly phosphorylating Ghd7 and OsPRR37; this modification delays heading date in non-inductive long-day conditions (Hori et al 2013 ; Kwon et al 2015 ). This suggests that the targets downstream of EL1/CKI act throughout various genetic and signaling pathways during rice development, such as inflorescence formation, flowering, stem elongation, and germination.…”

“…In our previous study, we isolated heterogeneous inbred family-near isogenic lines (HNILs) from a F 7 recombinant inbred line (RIL) heterozygous for the functional EL1 allele and the nonfunctional el1 allele (Kwon et al 2014 ). The natural missense mutation in el1 promotes flowering under non-inductive long-day conditions due to a defect in the protein kinase activity (Kwon et al 2014 , 2015 ). In this study, we found that the HNILs possessing EL1 or el1 showed different inflorescence and spikelet fertility phenotypes.…”